In the field of this invention it is known to provide either IQ modulation or FM (Frequency Modulation) direct PLL (Phase Locked Loop) modulation as separate types of modulation techniques, each with its own dedicated circuitry.
However, this approach has the disadvantage(s) that if a single circuit is desired to provide multi-mode operation (i.e., operation in any of a desired range of communications protocols requiring different modulation schemes, e.g., GSM (General System for Mobile communications), Bluetooth, HomeRF, AMPS (Advanced Mobile Phone Service), TETRA (Terrestrial Trunked Radio), CDMA (Code Division Multiple Access), etc.), the need to provide multiple modulation circuits for multiple possible modulation schemes significantly increases cost and power consumption.
As an example, if a GSM-only radio mode is required, then FM modulation would be used. If GSM and EDGE modulation are required where an IQ modulator is needed for EDGE, then GSM modulation through an IQ modulator rather FM modulator would be used, assuming that the RF IQ modulator meets the receiver noise requirements to avoid using a TX filter or duplexer.
A need therefore exists for having an FM modulation and/or an IQ modulation on the same transceiver circuit, and for a waveform generator for use in IQ modulation wherein the abovementioned disadvantage(s) may be alleviated.